This invention relates to the handling of marine cargoes, and particularly cargoes of fragmented metal such as ferrous metal turnings and pre-crushed sponge iron.
Ferrous turnings are a form of metal scrap generated in various machine shop operations and then crushed or processed in other ways to prepare them for shipment and remelting in a furnace. As normally collected by scrap dealers and available commercially, they are a heterogenous mixture of many types of carbon steels and contain minor amounts of various cutting oils and coolants. The turnings can be contaminated with cast iron borings, rust, non-ferrous metals, and organic materials. Pre-crushed sponge iron comprises porous pellets, lumps, and briquettes of direct reduced iron.
Ferrous turnings and pre-crushed iron when stored can generate heat by undergoing exothermic reactions. This is particularly true when a large mass of these materials is piled together in a confined space, as for example a ship's hold. A ship's hold can contain in excess of 2,000 long tons of turnings, and often from 10,000 to 20,000 long tons of turnings. The exact nature of the exothermic reactions while a pile of turnings undergoes is not known. However, it is believed that heat is generated due to rusting of the steel, particularly when water is present, and decomposition of the cutting oils. It has been noted that volatile gases, including hydrogen, can be given off when a pile of turnings reaches an excessively high temperature in the neighborhood of 300.degree. to 400.degree. F.
For over thirty years, the tendency of a pile of turnings to heat up has been a serious problem for the shippping industry. The danger of a fire or explosion at sea or in port is of great concern. For example, on Jan. 21, 1970, a fire occurred in the Norwegian N.V. "Pontos" in Los Angeles due to turnings which had reached a temperature in excess of 500.degree. F. in the hold. A fire occurred in which the flames reached a height of 30 feet above the hatch coaming. The vessel was saved only by flooding the hold with water and unloading the turnings from the vessel.
Until my invention, which is described below, there has been no satisfactory solution to the problem. The solution used by the U.S. Coast Guard is to prevent a vessel from sailing if the turnings in the hold have an excessively high temperature. This means that a ship loaded with hot turnings must sit in port, with the hold open, until the turnings cool down by heat transferred to the surroundings. According to Title 36 of the U.S. Code of Federal Regulations, Section 148.04-13, which deals with loading of metal borings, shavings, turnings, and cuttings into a ship, these materials cannot be loaded if the temperature of the material is not less than 130.degree. F. Furthermore, the vessel cannot leave port unless "the temperature of each article in each hold is less than 150.degree. F. and, if the temperature of the article in the hold has been more than 150.degree. F. during loading, the temperature of each article has shown a downward trend below 150.degree. F. for at least 8 hours after completion of loading of the hold . . . "
Waiting in port for turnings to cool can be very expensive. Vessels have had to sit in port for one to two months at costs well in excess of $100,000 while waiting for turnings to cool. In addition, the turnings can carbonize due to the heat, thereby rendering the turnings useless. Since turnings are currently worth about $140 per ton, carbonization of 5,000 tons of turnings can be costly.
In spite of the precautions mandated by the Coast Guard, the danger of fires from hot turnings remains a potentially serious problem. In response to this danger, the Canadian government has banned ships carrying turnings from the St. Lawrence Seaway. The Canadian government is concerned that a ship carrying turnings could catch fire and explode in one of the locks, and thereby close down the seaway. Such a regulation is also under consideration for the Panama Canal. Furthermore, because of the danger of fires, insurance underwriters charge a premium for ships carrying turnings.
In view of the above, there is a need for a method for preventing turnings from heating up in a ship's hold, and for a method for cooling down hot turnings.